Volcanic perturbations of the marine environment in South China preceding the latest Permian mass extinction and their biotic effects

ABSTRACT The Dongpan section in southern Guangxi Province records the influence of local volcanic activity on marinesedimentation at intermediate water depths ( 200–500 m) in the Nanpanjiang Basin (South China) during thelate Permian crisis. We analyzed 100 samples over a 12-m-thick interval, generating palynological, paleobio-logical, and geochemical datasets to investigate the nature and causes of environmental changes. The sectionrecords at least two major volcanic episodes that culminated in deposition of approximately 25- to 35-cm-thickash layers (bentonites) and that had profound effects on conditions in both the Dongpan marine environmentand adjacent land areas. Intensification of eruptive activity during each volcanic cycle resulted in a shift towardconifer forests, increased wildfire intensity, and elevated subaerial weathering fluxes. The resulting increase innutrientfluxesstimulated marineproductivityin the shortterm butled to a negativefeedbackonproductivityinthe longer term as the OMZ of the Nanpanjiang Basin expanded, putting both phytoplankton and zooplanktoncommunities under severe stress. Radiolarians exhibit large declines in diversity and abundance well before theglobalmass extinctionhorizon,demonstratingthe diachroneityofthe marine bioticcrisis.Thelatest Permian cri-sis,whichwasprobablytriggeredbytheSiberianTrapsfloodbasalts,intensifiedthedestructiveeffectsoftheear-lierlocaleruptionsonterrestrialandmarineecosystemsoftheSouthChinacraton.Received26April2011;accepted6October2011Corresponding author. Q. Feng. Tel.: +8618971193331; fax: +8602767883002; e-mail: qinglaifeng@cug.edu.cn